The invention relates to chip cards and, more especially, to cards in which the integrated circuit chip comprises not only a microprocessor and a program read-only memory (that cannot be changed) but also an electrically programmable memory that is capable of storing not only data but also a code that can be executed by the microprocessor.
These memory cards are useful notably for applications having a hierarchy of several possible functions. For example, the manufacturer of the integrated circuit chip will set up programs for the operation of the microprocessor at a first level of functions. In particular, he will set up all the programs of the read-only memory which are definitively fixed. The chip card manufacturer who incorporates the integrated circuit into his card will set up a second level of functions. The institution (the bank or purveyor of services) which is the customer of the chip card manufacturer will set up a third level of functions, and the final user (the customer of the purveyor of services) will finally be able to use a fourth level of functions. This theoretical hierarchy is given only as an example.
According to the invention, a particularly easy means has been found, making it possible to have several different functions that are accessible to different levels of use.